Against the background of rapid global urbanization, the renewal and renovation of historic districts have become an increasingly important concern. As a city with a long and rich history, Beijing contains numerous historic districts that are in urgent need of systematic renewal and renovation. This study proposes a functional enhancement and renovation design methodology for urban historic districts based on space syntax theory and analytical methods, applying it to the Qianmen Historic District in Beijing. Through traffic flow and business format analysis, the research examines traffic patterns and business format distribution characteristics in the Qianmen area and ultimately guides the design based on these findings. Research indicates that restrooms and attractions in Beijing’s Qianmen historic district exhibit dispersed space distribution, broad service coverage, high metric step depth (447 m and 436 m, respectively), and low topological connectivity. In contrast, hotels and restaurants feature smaller service areas, lower metric step depth (395 m and 297 m, respectively), and higher topological connectivity. Based on these findings, this study proposes targeted design recommendations for Qianmen’s street renovations based on traffic flow analysis results. Considering the need for vehicle parking and pedestrian rest demands in urban functional renewal, rest seats and shared charging piles are set up on the streets with big pedestrian flow to meet the needs of pedestrians. Moreover, cycling routes are designed to connect big-traffic-flow streets with small-traffic-flow ones. These renewal measures aim to enhance the overall vitality of the Qianmen district. The renovation approach and methodology proposed in this study can serve as a reference for future updates and renovations of historic districts.

The attention to environmental sustainability and energy has progressively increased in recent years, driven by the global energy crisis and mounting climate change concerns

As global climate change intensifies and energy crises deepen, photovoltaic (PV) applications in cities are increasingly garnering attention worldwide. In this context, retrofitting existing high-density residential areas with PV applications is becoming a focus of urban low-carbon development. As the most densely populated city in Western China, Chengdu is characterized by rapid development and high energy consumption. The widespread application of photovoltaic (PV) systems could significantly alleviate its energy consumption issues. This research investigated the PV application potentials of 27 non-residential areas in high-density residential areas in Chengdu, Sichuan Province from a design perspective and proposed design recommendations for PV applications in these spaces. In addition, this study analyzed urban morphological factors affecting the PV generation potential in non-residential areas through a Pearson correlation. The key factors influencing the PV application potential in these areas were building density (BD), non-residential area perimeter-to-area ratio (NBPAR), and maximum building height (H_max). This research aims to provide new strategies and methods for the low-carbon transformation of future urban high-density residential areas.

Photovoltaic (PV) technology has made significant progress since the International Energy Agency (IEA) proposed the concept of PV application in the built environment in 1997. This paper reviews PV applications in the built environment across three phases: pre-design, design, and post-design. A PRISMA-informed search was conducted in Web of Science Core Collection and Scopus, covering publications from January 2005 to August 2026. After screening, 211 publications were included in the review, and 238 references were cited in total, including 27 pre-2005 background sources. In the pre-design phase, the scopes and impacts of PV application in the built environment are reviewed. In the design phase, design strategies are examined in terms of PV module selection, mounting configuration, array layout, and geometric design parameters. In the post-design phase, power potential, economic potential, aesthetic environment, and safety reporting are reviewed. Based on these findings, a consultative and iterative design workflow is proposed. It integrates stakeholder priorities, multi-scale spatial data, climate-specific economic parameters, and construct-specific aesthetic and social evaluation. However, the workflow is conceptual and has not yet been empirically validated. Its potential to improve public acceptance and facilitate implementation therefore requires future testing in real projects. The review provides a structured reference for urban planners, architects, and developers, while highlighting the need for empirical validation before large-scale application.

Large-scale electrification of urban bus fleets requires coordinated depot siting, route assignment, photovoltaic (PV) deployment, charging infrastructure, and battery storage operation. A two-stage framework is developed for planning and operating PV-assisted electric bus depots. Stage 1 uses a lexicographic mixed-integer linear programming model that first minimizes depot construction investment and then minimizes route-depot deadheading energy cost within the minimum-investment solution class. Stage 2 uses depot-level dynamic programming to schedule hourly PV generation, bus charging loads, station batteries, and grid exchange while enforcing energy balance, state-of-charge (SOC) continuity and limits, power limits, terminal SOC restoration, zero unserved demand, mutually exclusive battery charging and discharging, and no simultaneous grid buying and selling. Controlled low-price grid-to-battery charging is allowed only after direct PV-to-bus, PV-to-battery, battery-to-bus, and grid-to-bus supply are accounted for. Using site-specific PV estimates for 44 Haidian depots and operating data for 52 routes, the solution selects 12 depots, 140 charging piles, and 11,333.6 kWh of storage. The selected depots provide 68,107.4 kWh/day of PV potential for 67,671.6 kWh/day of assigned charging demand. The daily net dispatch cost is 1,209.9 yuan/day, unserved demand is zero, and the 25-year lifecycle cost is 105.28 million yuan. Storage lowers lifecycle cost by about 25.5 million yuan in the total-cost and construction-cost schemes. The charging-cost-oriented sensitivity case also shows that export-capacity or PV-deployment constraints are required when many PV-rich depots are opened.